Research at RERI: Species Distribution in Hydrocarbon Reservoirs from Irreversible Thermodynamics

Irreversible thermodynamics can be used to formulate the various diffusion processes. One important diffusion flux in the subsurface is thermal diffusion due to the thermal field. Another important diffusion is pressure diffusion arising from long fluid columns. All the three diffusion processes (Fickian, thermal, and pressure) as well as natural convection may affect species distribution in the subsurface. Of particular complexity in oil and gas reservoirs is the multicomponent nature of the fluids and lack of established theories in the literature. The focus of our work is in relation to diffusions. We perform experimental research mainly limited to the laser beam technique. We also do theoretical and molecular simulations with molecular dynamics simulations being used to understand diffusion in the critical region modeling.

Higher Density Fluid Floating at the Top

Ghorayeb, K., Firoozabadi, A., and Anraku, T.: "Interpretation of the Unusual Fluid Distribution in the Yufutsu Gas-Condensate Field," SPE J (2003) 8(2), 114-123.

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In the subsurface cavity, the density of the fluid at the top is higher than the fluid density below. In open wells, there is a liquid in the middle with higher density than at the top and bottom.